Spin Orbit Torque Magnetic Random Access Memory Research Articles

Ultra-Fast Switching of a Free Magnetic Layer with Out-of-Plane Magnetization in Spin-Orbit Torque MRAM Cells

The steady increase in performance and speed of modern integrated circuits is continuously supported by constant miniaturization of complementary metal-oxide semiconductor devices. However, the rapid growth of the dynamic and stand-by power due to transistor leakages becomes a pressing issue. A promising way to interrupt this trend is to introduce non-volatility. The development of an electrically addressable non-volatile memory combining high speed and high endurance is essential for achieving these goals. The perpendicular spin-orbit torque magnetic random access memory (SOT-MRAM) combines non-volatility, high speed, and high endurance and is thus suitable for applications in caches. However, its development is still hindered by the necessity of a static in-plane magnetic field. We propose a magnetic field-free perpendicular SOT-MRAM, operated by two consecutive perpendicular current pulses, which is fast and, most importantly, does not require an external magnetic field.

Area-Efficient SOT-MRAM With a Schottky Diode

This letter presents a spin-orbit torque magnetic random access memory (SOT-MRAM) for high-density, reliable, and energy-efficient on-chip memory application. Unlike the conventional SOT-MRAM requiring two access transistors, the proposed MRAM uses only one access transistor along with a Schottky diode in order to achieve high integration density while maintaining the advantages of SOT-MRAM, such as low write energy and enhanced reliability of magnetic tunnel junction. The Schottky diode is forward-biased during read, whereas it is reverse-biased during write to prevent sneak current paths. Our simulation results show that the proposed MRAM can achieve 30% and 50% reduction in bit-cell area in comparison to conventional spin-transfer torque MRAM (STT-MRAM) and SOT-MRAM, respectively, and $\sim 2.5\times $ improvement in write power compared with the STT-MRAM.

Perpendicular Magnetic Anisotropy on W-based Spin-Orbit Torque CoFeB | MgO MRAM Stacks

ABSTRACTWe study W | Ta | CoFeB | MgO stacks for spin-orbit torque MRAM applications. A strong perpendicular magnetic anisotropy is obtained after annealing for CoFeB layer thickness of 0.9 nm or 1.2 nm and for specific W/Ta ratios, were the Ta layer thickness is between 0.3 nm and 1 nm. Furthermore, the desired high-spin orbit coupling β-phase of W is preserved even after annealing at 350°C. We argue that an efficient B getter, like Ta, is necessary for the coherent crystallization of the CoFeB | MgO interface that allows for the establishment of perpendicular magnetic anisotropy.